The invention relates to the production of bulky continuous filament yarn and more particularly, it relates to air-jet-textured yarns known as core-and-effect yarns.
Among many types of continuous filament synthetic yarns which simulate the bulk and feeling of spun staple yarns, one of the more successful types is that which has been air-textured in a jet at an overfeed to loop and entangle the filaments, as disclosed in Breen U.S. Pat. No. 2,783,609. One version of such yarns is known as core-and-effect, wherein one or more yarns are fed to the texturing jet at a low degree of overfeed and one or more additional yarns are fed at a higher degree of overfeed so that the first or core yarn is untextured and supports the tension imposed on the fabric while the second or effect yarn forms the surface loops which contribute the spun-like character.
Prior art core-and-effect yarns are comprised of relatively low-denier core yarn to provide modest tensile strength and a relatively higher denier effect yarn to impart high bulk or some novel feature such as a boucle effect. The effect yarns constitute half or more of the total yarn denier. The effect yarn overfeed has usually been 70 percent or more to maximize bulk and texture. However, the relatively low breaking strength of prior art core-and-effect yarns makes them generally unattractive for most industrial end uses.
Such industrial end uses include the fabric reinforcement in fire hoses or V-belts, where high strength is the most important requirement and only a modest amount of texture is needed to improve the adhesion between the fabric and rubber. In other applications, the webbing straps and covering of knapsacks, for example, require high tenacity for strength with light weight. Texture is needed to prevent warp and weft yarns from shifting under high loads so that the knapsack will retain its proper shape. In apparel uses such as denim for work trousers, strength is the primary requirement and only a small amount of texture is needed to provide spun-like aesthetics and retain shape. Spun hand is desirable in most apparel end uses.
One type of yarn which has been used for such purposes has been made by passing high-tenacity, continuous filament nylon or polyester yarn through an air texturing jet at overfeeds of 7 to 43 percent as disclosed in Gage U.S. Pat. No. 3,433,008. Since each filament of such yarns forms crunodal loops, the load bearing strength depends on the tightness of entanglement of the filaments and the frictional forces between filaments, which govern the load at which the filaments begin to slide past each other and the crunodal loops begin to disappear.
Lower yarn initial modulus and higher yarn breaking elongation, irreversible bulk losses when yarns are subjected to loads, and proportionately lower yarn breaking strengths (vs. component feed yarn) are a direct consequence of this phenomenon. Optimum selection of yarn finish is critical since high finish levels and high lubricity finishes generally reduce yarn bulk stability. The Gage patent requires a special high friction finish which may not be optimum for best operability in fabric-making processes.
Breaking strength of the textured yarn is seldom greater than 60 percent of the breaking strength of the component yarn and often as low as 45 percent.
It has now been found that yarns with both high tenacity and spun-like hand may be made by core-and-effect texturing using a particular selection of untextured supply yarns and texturing conditions.
These yarns overcome many of the negative features associated with single- and parallel-end air textured yarns. Specifically, yarns of this invention generally have breaking strengths 80 percent to 90 percent of the component core yarn; bulk stability is insensitive to yarn finish; and bulked yarns have higher initial moduli and lower breaking elongations than corresponding parallel air textured yarns. These yarns do not lose their texture until the core yarn reaches its breaking point.